Transformer gins are devices which may be attached to a utility pole to facilitate raising or lowering of electrical distribution transformers with respect to the pole. Such transformers, which usually weigh about 300 to 850 pounds, are typically mounted near the top of the pole between the primary and secondary voltage power lines supported by the pole. Conventional transformer gins include a supporting arrangement which must be releasably attached to the pole above the transformer and a hoist such as a block and tackle rig or a sling which is suspended from the support to carry the weight of the transformer as it is raised or lowered with respect to the pole with the aid of a power operated winch.
The authorities responsible for ensuring safe working conditions for high voltage linemen have established "limits of approach" which are the minimum distances to which qualified personnel may approach live electrical lines and/or apparatus in the absence of approved protective equipment barriers and/or devices. For example, qualified employees of the British Columbia Hydro and Power Authority may approach 12,000 volt conductors and/or apparatus to within no more than 0.9 meters when working with uninsulated aerial lifting equipment or the like. Such employees may approach 25,000 volt conductors to within no more than 1.2 meters when working under such conditions. However, the mounting distance between a distribution transformer and the overhead primary voltage power lines is typically such that conventional transformer gins cannot be used without encroaching upon the aforementioned limits of approach. Frequently, for example, the gin supporting arms protrude upwardly from their point of attachment to the utility pole to provide sufficient clearance for the block and tackle or other hoist means from which the transformer is suspended. This can clearly be seen, for example, in FIG. 1 of U.S. Pat. No. 2,833,423 granted May, 6 1958 for an invention of J. A. Tucker.
In many practical situations the distance between the top of the distribution transformer and the overhead primary voltage power lines will be such that devices of the type exemplified in the Tucker patent cannot be used without encroaching upon the aforementioned limits of approach. Accordingly, such devices can frequently only be used by following a rigorous safety procedure which requires the cooperation of the utility authorities (who would, for example, deactivate any circuit reclosing devices in the electrical circuit which includes the particular distribution transformer), the presence of at least two qualified linemen and the use of special protective equipment. This increases the cost and time required to install, remove or replace a distribution transformer which, by itself, is a relatively simple task.
The present invention provides a material hoisting gin which is particularly well suited to use as a transformer gin. More specifically, the invention provides a transformer gin which requires only minimal operating clearance above the distribution transformer; thereby maximizing the likelihood that the gin may be used without encroaching upon the limits of approach to the overhead power lines. Furthermore, the gin is light in weight and can be used quickly, safely and effectively by a single man.